1. Technical Field
The present invention relates to a method for forming an organic semiconductor film and an organic semiconductor film, and a method for producing an organic thin-film transistor.
2. Background
In recent years, various organic thin-film transistors, in which organic semiconductors are employed as a semiconductor channel, have been investigated. Organic semiconductors are more easily processed compared to inorganic semiconductors, and also exhibit high affinity to a plastic support, whereby they have received attention as a thin-film device.
Methods for forming an organic semiconductor film are represented by the method employing vapor deposition, and various methods are employed depending on characteristics of the materials. Under such situations, many trials have been made, which intends to more easily prepare an organic semiconductor film of enhanced carrier mobility, compared to vapor deposition, by employing a normal pressure process (being a wet process) which employs coating or application of a solution or a liquid composition onto a substrate.
For example, of trials to prepare organic semiconductor films employing solution layer lamination, enhancement of organic semiconductor polymer arrangement was tried via an orientation film (refer, for example, to Patent Document 1). Further, an organic semiconductor film or an organic semiconductor layer exhibiting high carrier mobility is formed in such a manner that a thiophene polymer solution exhibiting high mobility is employed and coating is carried out while drying solvents (refer, for example, to Non-patent Document 1).
However, during formation of the organic semiconductor layer, the carrier mobility is determined via crystals or the arrangement such as a n-stack of a structure body, whereby a problem occurs in which the mobility of the semiconductor layer prepared via the method in which an organic semiconductor solution is simply coated followed by drying solvents is still too low. Further, at the same time, pointed out are problems such as characteristic variation during repeated determination and the high threshold gate voltage.
Further, as problems during formation of a semiconductor layer, in order to enhance mobility, many low soluble semiconductor materials, such as pentacene, have been reported, which resulted in relatively high performance. Prospectively, in order to realize formation of a semiconductor layer via coating, highly soluble semiconductor materials have been increasingly developed. On the other hand, it is common knowledge that in order to enhance performance, those which are subjected to a surface treatment such as a surface hydrophobic treatment, are appropriate, while due to the above treatment, it has become more difficult to coat a semiconductor solution.    Patent Document 1: International Patent Publication No. 01/47043 Pamphlet    Non-patent Document 1: J. Am. Chem. Soc., 2004, 126, 3378